Most cameras are fitted with some form of protective cover for several reasons. The common exception is probably in small retail establishments where the risk of damage is slight.
Housings are used internally for a variety of reasons. Sometimes it is where the need is for the camera to be discrete. This could be in certain types of establishment where the security of customers or members is necessary. It may be that the impression of intrusion of privacy needs to be subtly avoided. There are housings designed to blend in with the decor for aesthetic purposes. These can be miniature cameras secreted in light fittings or ventilation grills. This type of housing is often used in hotels, museums and art galleries, shopping malls, etc.
Another range of housings is designed for covert surveillance. The intention of this housing is that it is not a deterrent but deliberately disguised as some innocuous common object. They usually incorporate a miniature camera fitted with a pinhole lens. These objects have been as diverse as PIRs, clocks, extractor fan controls, smoke detectors, etc. There appears no limit to the imaginative methods of concealing cameras.
Indoor cameras may sometimes have to be protected from attack and therefore fitted in vandal proof housings. This often takes the form of a wedge shaped housing fitted in a false ceiling with the minimum area projecting below.
The disadvantage of the wedge shaped housing is that it must be mounted facing in the correct direction. Once fitted it is not easy to change the orientation of the camera. This type of housing is often used when it is required to view along a corridor or other predetermined direction.
There may be situations where it is needed to have more flexibility in setting up the direction the camera is viewing. This requirement often also needs the direction being viewed to be discreet. The solution here is to use a type of domed housing. The dome can be either a hemisphere or a complete sphere. The hemispherical, or half dome, can be fitted in place of a standard ceiling tile. The camera is mounted on an adjustable platform that may be set for both angles of view and direction.
There are two main types of plastic used for the domes. One is a black acrylic material with a less dense slot through which the camera views. The other has a silvered coating on the inside and acts in the same as a one way mirror. With this type of enclosure, there is a great deal of flexibility in setting the camera view. It is also very easy and quick to change the direction of view through 360°.
These are often called weatherproof or environmental housings. There are standards that specify the degree of protection to be provided by enclosures. Mainly these are, BS 5490, IEC 529, DIN 40 050. The rating of protection is defined by two digits prefixed by the agreed letters IP. (In some countries three digits are used.) The letters stand for Ingress Protection, and the significance of the digits is as follows:
First digit: The degree of protection that is provided with respect to persons and to equipment inside the enclosure.
Second digit: The degree of protection that is provided with respect to the harmful ingress of water.
Third digit: The degree of mechanical protection.
For example, a rating of IP 54 indicates class 5 protection against the ingress of dust and class 4 against the entry of moisture. Camera housings used in the UK will usually have a rating of IP 65 or IP 66.
Note that these ratings only apply to normal environmental conditions. Special protection is required for areas such as refineries, mines, flour mills, etc. If there is any doubt the customer will be aware of special conditions applying to particular parts of the site.
Tables 10.1and 10.2 at the end of this chapter list all the index numbers.
Selection of External Housings
Weatherproof housings must be about the most mundane aspect of a CCTV installation. Or so it seems, because many engineers simply consider the housing as a protection against the elements. However, there are many aspects to consider and many suppliers of housings. It is about the cheapest element of an external system yet price appears to be the main factor in selecting which to use. Important considerations should be:
- Ease of access for pre-assembly in the workshop.
- Ease of access during installation.
- Ease of access for future service needs.
- Is the camera mounting plate insulated from the case?
- Can the mechanical focusing screw on the camera be reached? Some are at the back, some at the side and some on top.
- Can the lens be focused and the peak/average settings adjusted on site?
- Can one man remove the cover and work on the inside?
- If there is a telemetry board fitted, can it be accessed without removing the camera?
This article is an extract from chapter 10 of 'The Principles & Practice of CCTV' which is recognised as the benchmark for CCTV installation in the UK.